Justification:
Listed as Least Concern because of its wide distribution, large population, occurrence in a number of protected areas, and lack of major threats; it is tolerant to habitat disturbance and its population is increasing.

This species is found in the eastern United States and adjacent southern Canada; southern Quebec to Manitoba, south to eastern Texas and Florida. Its range has been extended through introductions into Quebec, Ontario, New Brunswick, Manitoba, Saskatchewan, British Columbia, Nova Scotia, California, Oregon, Washington, and Montana (Teaford 1986, Koprowski 1994). It is also introduced in the British Isles, Italy, South Africa, and Australia (extirpated by 1973), but these introduced ranges are not included in the map here (Koprowski 1994).

It is found in large blocks of hardwood or mixed forests, as well as in urban and suburban areas. Prefers mature deciduous and mixed forests with abundant supplies of mast (e.g., acorns, hickory nuts). A diversity of nut trees is needed to support high densities. It also uses city parks and floodplains. Seldom far from permanent open water. In southern Alabama, narrow bands of hardwoods along ephemeral streams were an important component of the habitat in even-aged pine and mixed pine-hardwood stands. It rests in tree cavity or leaf nest; leaf nests apparently are made primarily by dispersing juveniles 18-19 weeks old. It nests in tree cavities or in leaf nests, usually 25 feet or more above the ground. Most winter-spring litters are born in tree cavities, most spring-summer litters in leaf nests (Teaford 1986). Cavities suitable for nesting are dry, 15-25 cm in diameter, 40-50 cm deep, with an entrance hole about eight cm in diameter (Teaford 1986). Females may move young from tree cavity nest to leaf nest, possibly to escape fleas.

In Illinois, most breeding occurs in December-February and May-June; slightly later in more northern latitudes (Koprowski 1994). One or two litters per year. First litter is produced mostly in February-March, sometimes as early as January in some areas; second litter, July or August. Gestation lasts 44 days. Litter size most often is 2-3. Young are tended by female. Weaning is completed at about 10-12 weeks (in spring and/or late summer-early autumn). Most breed as yearlings, sometimes sooner (as early as five months) or later. Reproductive output, including the percentage of adults that produce young and the number of litters per year, is positively correlated with mast abundance. Maximum reproductive longevity is about a decade.

Home range averages 0.5-10 ha, with older males tending to have the largest ranges (Teaford 1986); usually home range is less than five hectares (Koprowski 1994). Not territorial, home range overlap is extensive; social system is characterized by a linear dominance hierarchy. Disperses up to a few kilometres from natal area upon approaching sexual maturity. Large-scale one-way emigrations have been observed, generally coinciding with high population density and mast crop failure.

It is pray of many predators, but predation does not appear to limit populations (Teaford 1986). Mean annual mortality reported for adults is 42-57% (Koprowski 1994). Diet consists of seeds, fruits, nuts, fungi, occasional insects and small vertebrates (e.g., bird eggs). Scatterhoarder; buries nuts and acorn in autumn for later consumption (winter-spring). It is active during the day, particularly in the morning and late afternoon, though unimodal activity may occur in winter. May be inactive for a day or two during extremely cold, snowy weather.